//! This module implements some validity checks for attributes. //! In particular it verifies that `#[inline]` and `#[repr]` attributes are //! attached to items that actually support them and if there are //! conflicts between multiple such attributes attached to the same //! item. use crate::{errors, fluent_generated as fluent}; use rustc_ast::{ast, AttrStyle, Attribute, LitKind, MetaItemKind, MetaItemLit, NestedMetaItem}; use rustc_data_structures::fx::FxHashMap; use rustc_errors::{Applicability, IntoDiagnosticArg, MultiSpan}; use rustc_feature::{AttributeDuplicates, AttributeType, BuiltinAttribute, BUILTIN_ATTRIBUTE_MAP}; use rustc_hir as hir; use rustc_hir::def_id::LocalModDefId; use rustc_hir::intravisit::{self, Visitor}; use rustc_hir::{ self, FnSig, ForeignItem, HirId, Item, ItemKind, TraitItem, CRATE_HIR_ID, CRATE_OWNER_ID, }; use rustc_hir::{MethodKind, Target, Unsafety}; use rustc_macros::LintDiagnostic; use rustc_middle::hir::nested_filter; use rustc_middle::middle::resolve_bound_vars::ObjectLifetimeDefault; use rustc_middle::query::Providers; use rustc_middle::traits::ObligationCause; use rustc_middle::ty::error::{ExpectedFound, TypeError}; use rustc_middle::ty::{self, TyCtxt}; use rustc_session::lint::builtin::{ CONFLICTING_REPR_HINTS, INVALID_DOC_ATTRIBUTES, INVALID_MACRO_EXPORT_ARGUMENTS, UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES, UNUSED_ATTRIBUTES, }; use rustc_session::parse::feature_err; use rustc_span::symbol::{kw, sym, Symbol}; use rustc_span::{BytePos, Span, DUMMY_SP}; use rustc_target::spec::abi::Abi; use rustc_trait_selection::infer::{TyCtxtInferExt, ValuePairs}; use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt; use rustc_trait_selection::traits::ObligationCtxt; use std::cell::Cell; use std::collections::hash_map::Entry; #[derive(LintDiagnostic)] #[diag(passes_diagnostic_diagnostic_on_unimplemented_only_for_traits)] pub struct DiagnosticOnUnimplementedOnlyForTraits; pub(crate) fn target_from_impl_item<'tcx>( tcx: TyCtxt<'tcx>, impl_item: &hir::ImplItem<'_>, ) -> Target { match impl_item.kind { hir::ImplItemKind::Const(..) => Target::AssocConst, hir::ImplItemKind::Fn(..) => { let parent_def_id = tcx.hir().get_parent_item(impl_item.hir_id()).def_id; let containing_item = tcx.hir().expect_item(parent_def_id); let containing_impl_is_for_trait = match &containing_item.kind { hir::ItemKind::Impl(impl_) => impl_.of_trait.is_some(), _ => bug!("parent of an ImplItem must be an Impl"), }; if containing_impl_is_for_trait { Target::Method(MethodKind::Trait { body: true }) } else { Target::Method(MethodKind::Inherent) } } hir::ImplItemKind::Type(..) => Target::AssocTy, } } #[derive(Clone, Copy)] enum ItemLike<'tcx> { Item(&'tcx Item<'tcx>), ForeignItem, } #[derive(Copy, Clone)] pub(crate) enum ProcMacroKind { FunctionLike, Derive, Attribute, } impl IntoDiagnosticArg for ProcMacroKind { fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> { match self { ProcMacroKind::Attribute => "attribute proc macro", ProcMacroKind::Derive => "derive proc macro", ProcMacroKind::FunctionLike => "function-like proc macro", } .into_diagnostic_arg() } } struct CheckAttrVisitor<'tcx> { tcx: TyCtxt<'tcx>, // Whether or not this visitor should abort after finding errors abort: Cell, } impl CheckAttrVisitor<'_> { /// Checks any attribute. fn check_attributes( &self, hir_id: HirId, span: Span, target: Target, item: Option>, ) { let mut doc_aliases = FxHashMap::default(); let mut specified_inline = None; let mut seen = FxHashMap::default(); let attrs = self.tcx.hir().attrs(hir_id); for attr in attrs { if attr.path_matches(&[sym::diagnostic, sym::on_unimplemented]) { self.check_diagnostic_on_unimplemented(attr.span, hir_id, target); } match attr.name_or_empty() { sym::do_not_recommend => self.check_do_not_recommend(attr.span, target), sym::inline => self.check_inline(hir_id, attr, span, target), sym::coverage => self.check_coverage(hir_id, attr, span, target), sym::non_exhaustive => self.check_non_exhaustive(hir_id, attr, span, target), sym::marker => self.check_marker(hir_id, attr, span, target), sym::target_feature => self.check_target_feature(hir_id, attr, span, target, attrs), sym::thread_local => self.check_thread_local(attr, span, target), sym::track_caller => { self.check_track_caller(hir_id, attr.span, attrs, span, target) } sym::doc => self.check_doc_attrs( attr, hir_id, target, &mut specified_inline, &mut doc_aliases, ), sym::no_link => self.check_no_link(hir_id, &attr, span, target), sym::export_name => self.check_export_name(hir_id, &attr, span, target), sym::rustc_layout_scalar_valid_range_start | sym::rustc_layout_scalar_valid_range_end => { self.check_rustc_layout_scalar_valid_range(&attr, span, target) } sym::allow_internal_unstable => { self.check_allow_internal_unstable(hir_id, &attr, span, target, &attrs) } sym::debugger_visualizer => self.check_debugger_visualizer(&attr, target), sym::rustc_allow_const_fn_unstable => { self.check_rustc_allow_const_fn_unstable(hir_id, &attr, span, target) } sym::rustc_std_internal_symbol => { self.check_rustc_std_internal_symbol(&attr, span, target) } sym::naked => self.check_naked(hir_id, attr, span, target), sym::rustc_never_returns_null_ptr => { self.check_applied_to_fn_or_method(hir_id, attr, span, target) } sym::rustc_legacy_const_generics => { self.check_rustc_legacy_const_generics(hir_id, &attr, span, target, item) } sym::rustc_lint_query_instability => { self.check_rustc_lint_query_instability(hir_id, &attr, span, target) } sym::rustc_lint_diagnostics => { self.check_rustc_lint_diagnostics(hir_id, &attr, span, target) } sym::rustc_lint_opt_ty => self.check_rustc_lint_opt_ty(&attr, span, target), sym::rustc_lint_opt_deny_field_access => { self.check_rustc_lint_opt_deny_field_access(&attr, span, target) } sym::rustc_clean | sym::rustc_dirty | sym::rustc_if_this_changed | sym::rustc_then_this_would_need => self.check_rustc_dirty_clean(&attr), sym::rustc_coinductive | sym::rustc_must_implement_one_of | sym::rustc_deny_explicit_impl | sym::const_trait => self.check_must_be_applied_to_trait(&attr, span, target), sym::cmse_nonsecure_entry => { self.check_cmse_nonsecure_entry(hir_id, attr, span, target) } sym::collapse_debuginfo => self.check_collapse_debuginfo(attr, span, target), sym::must_not_suspend => self.check_must_not_suspend(&attr, span, target), sym::must_use => self.check_must_use(hir_id, &attr, target), sym::rustc_pass_by_value => self.check_pass_by_value(&attr, span, target), sym::rustc_allow_incoherent_impl => { self.check_allow_incoherent_impl(&attr, span, target) } sym::rustc_has_incoherent_inherent_impls => { self.check_has_incoherent_inherent_impls(&attr, span, target) } sym::ffi_pure => self.check_ffi_pure(attr.span, attrs, target), sym::ffi_const => self.check_ffi_const(attr.span, target), sym::ffi_returns_twice => self.check_ffi_returns_twice(attr.span, target), sym::rustc_const_unstable | sym::rustc_const_stable | sym::unstable | sym::stable | sym::rustc_allowed_through_unstable_modules | sym::rustc_promotable => self.check_stability_promotable(&attr, span, target), sym::link_ordinal => self.check_link_ordinal(&attr, span, target), sym::rustc_confusables => self.check_confusables(&attr, target), sym::rustc_safe_intrinsic => { self.check_rustc_safe_intrinsic(hir_id, attr, span, target) } _ => true, }; // lint-only checks match attr.name_or_empty() { sym::cold => self.check_cold(hir_id, attr, span, target), sym::link => self.check_link(hir_id, attr, span, target), sym::link_name => self.check_link_name(hir_id, attr, span, target), sym::link_section => self.check_link_section(hir_id, attr, span, target), sym::no_mangle => self.check_no_mangle(hir_id, attr, span, target), sym::deprecated => self.check_deprecated(hir_id, attr, span, target), sym::macro_use | sym::macro_escape => self.check_macro_use(hir_id, attr, target), sym::path => self.check_generic_attr(hir_id, attr, target, Target::Mod), sym::macro_export => self.check_macro_export(hir_id, attr, target), sym::ignore | sym::should_panic => { self.check_generic_attr(hir_id, attr, target, Target::Fn) } sym::automatically_derived => { self.check_generic_attr(hir_id, attr, target, Target::Impl) } sym::no_implicit_prelude => { self.check_generic_attr(hir_id, attr, target, Target::Mod) } sym::rustc_object_lifetime_default => self.check_object_lifetime_default(hir_id), sym::proc_macro => { self.check_proc_macro(hir_id, target, ProcMacroKind::FunctionLike) } sym::proc_macro_attribute => { self.check_proc_macro(hir_id, target, ProcMacroKind::Attribute); } sym::proc_macro_derive => { self.check_generic_attr(hir_id, attr, target, Target::Fn); self.check_proc_macro(hir_id, target, ProcMacroKind::Derive) } _ => {} } let builtin = attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name)); if hir_id != CRATE_HIR_ID { if let Some(BuiltinAttribute { type_: AttributeType::CrateLevel, .. }) = attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name)) { match attr.style { ast::AttrStyle::Outer => self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::OuterCrateLevelAttr, ), ast::AttrStyle::Inner => self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::InnerCrateLevelAttr, ), } } } if let Some(BuiltinAttribute { duplicates, .. }) = builtin { check_duplicates(self.tcx, attr, hir_id, *duplicates, &mut seen); } self.check_unused_attribute(hir_id, attr) } self.check_repr(attrs, span, target, item, hir_id); self.check_used(attrs, target); } fn inline_attr_str_error_with_macro_def(&self, hir_id: HirId, attr: &Attribute, sym: &str) { self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::IgnoredAttrWithMacro { sym }, ); } fn inline_attr_str_error_without_macro_def(&self, hir_id: HirId, attr: &Attribute, sym: &str) { self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::IgnoredAttr { sym }, ); } /// Checks if `#[do_not_recommend]` is applied on a trait impl. fn check_do_not_recommend(&self, attr_span: Span, target: Target) -> bool { if let Target::Impl = target { true } else { self.tcx.sess.emit_err(errors::IncorrectDoNotRecommendLocation { span: attr_span }); false } } /// Checks if `#[diagnostic::on_unimplemented]` is applied to a trait definition fn check_diagnostic_on_unimplemented(&self, attr_span: Span, hir_id: HirId, target: Target) { if !matches!(target, Target::Trait) { self.tcx.emit_spanned_lint( UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES, hir_id, attr_span, DiagnosticOnUnimplementedOnlyForTraits, ); } } /// Checks if an `#[inline]` is applied to a function or a closure. Returns `true` if valid. fn check_inline(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) -> bool { match target { Target::Fn | Target::Closure | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true, Target::Method(MethodKind::Trait { body: false }) | Target::ForeignFn => { self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::IgnoredInlineAttrFnProto, ); true } // FIXME(#65833): We permit associated consts to have an `#[inline]` attribute with // just a lint, because we previously erroneously allowed it and some crates used it // accidentally, to be compatible with crates depending on them, we can't throw an // error here. Target::AssocConst => { self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::IgnoredInlineAttrConstants, ); true } // FIXME(#80564): Same for fields, arms, and macro defs Target::Field | Target::Arm | Target::MacroDef => { self.inline_attr_str_error_with_macro_def(hir_id, attr, "inline"); true } _ => { self.tcx.sess.emit_err(errors::InlineNotFnOrClosure { attr_span: attr.span, defn_span: span, }); false } } } /// Checks if a `#[coverage]` is applied directly to a function fn check_coverage(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) -> bool { match target { // #[coverage] on function is fine Target::Fn | Target::Closure | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true, // function prototypes can't be covered Target::Method(MethodKind::Trait { body: false }) | Target::ForeignFn => { self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::IgnoredCoverageFnProto, ); true } Target::Mod | Target::ForeignMod | Target::Impl | Target::Trait => { self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::IgnoredCoveragePropagate, ); true } Target::Expression | Target::Statement | Target::Arm => { self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::IgnoredCoverageFnDefn, ); true } _ => { self.tcx.sess.emit_err(errors::IgnoredCoverageNotCoverable { attr_span: attr.span, defn_span: span, }); false } } } fn check_generic_attr( &self, hir_id: HirId, attr: &Attribute, target: Target, allowed_target: Target, ) { if target != allowed_target { self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::OnlyHasEffectOn { attr_name: attr.name_or_empty(), target_name: allowed_target.name().replace(' ', "_"), }, ); } } /// Checks if `#[naked]` is applied to a function definition. fn check_naked(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) -> bool { match target { Target::Fn | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true, // FIXME(#80564): We permit struct fields, match arms and macro defs to have an // `#[allow_internal_unstable]` attribute with just a lint, because we previously // erroneously allowed it and some crates used it accidentally, to be compatible // with crates depending on them, we can't throw an error here. Target::Field | Target::Arm | Target::MacroDef => { self.inline_attr_str_error_with_macro_def(hir_id, attr, "naked"); true } _ => { self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn { attr_span: attr.span, defn_span: span, on_crate: hir_id == CRATE_HIR_ID, }); false } } } /// Checks if `#[cmse_nonsecure_entry]` is applied to a function definition. fn check_cmse_nonsecure_entry( &self, hir_id: HirId, attr: &Attribute, span: Span, target: Target, ) -> bool { match target { Target::Fn | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true, _ => { self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn { attr_span: attr.span, defn_span: span, on_crate: hir_id == CRATE_HIR_ID, }); false } } } /// Debugging aid for `object_lifetime_default` query. fn check_object_lifetime_default(&self, hir_id: HirId) { let tcx = self.tcx; if let Some(owner_id) = hir_id.as_owner() && let Some(generics) = tcx.hir().get_generics(owner_id.def_id) { for p in generics.params { let hir::GenericParamKind::Type { .. } = p.kind else { continue }; let default = tcx.object_lifetime_default(p.def_id); let repr = match default { ObjectLifetimeDefault::Empty => "BaseDefault".to_owned(), ObjectLifetimeDefault::Static => "'static".to_owned(), ObjectLifetimeDefault::Param(def_id) => tcx.item_name(def_id).to_string(), ObjectLifetimeDefault::Ambiguous => "Ambiguous".to_owned(), }; tcx.sess.emit_err(errors::ObjectLifetimeErr { span: p.span, repr }); } } } /// Checks if `#[collapse_debuginfo]` is applied to a macro. fn check_collapse_debuginfo(&self, attr: &Attribute, span: Span, target: Target) -> bool { match target { Target::MacroDef => true, _ => { self.tcx .sess .emit_err(errors::CollapseDebuginfo { attr_span: attr.span, defn_span: span }); false } } } /// Checks if a `#[track_caller]` is applied to a non-naked function. Returns `true` if valid. fn check_track_caller( &self, hir_id: HirId, attr_span: Span, attrs: &[Attribute], span: Span, target: Target, ) -> bool { match target { _ if attrs.iter().any(|attr| attr.has_name(sym::naked)) => { self.tcx.sess.emit_err(errors::NakedTrackedCaller { attr_span }); false } Target::Fn | Target::Method(..) | Target::ForeignFn | Target::Closure => true, // FIXME(#80564): We permit struct fields, match arms and macro defs to have an // `#[track_caller]` attribute with just a lint, because we previously // erroneously allowed it and some crates used it accidentally, to be compatible // with crates depending on them, we can't throw an error here. Target::Field | Target::Arm | Target::MacroDef => { for attr in attrs { self.inline_attr_str_error_with_macro_def(hir_id, attr, "track_caller"); } true } _ => { self.tcx.sess.emit_err(errors::TrackedCallerWrongLocation { attr_span, defn_span: span, on_crate: hir_id == CRATE_HIR_ID, }); false } } } /// Checks if the `#[non_exhaustive]` attribute on an `item` is valid. Returns `true` if valid. fn check_non_exhaustive( &self, hir_id: HirId, attr: &Attribute, span: Span, target: Target, ) -> bool { match target { Target::Struct | Target::Enum | Target::Variant => true, // FIXME(#80564): We permit struct fields, match arms and macro defs to have an // `#[non_exhaustive]` attribute with just a lint, because we previously // erroneously allowed it and some crates used it accidentally, to be compatible // with crates depending on them, we can't throw an error here. Target::Field | Target::Arm | Target::MacroDef => { self.inline_attr_str_error_with_macro_def(hir_id, attr, "non_exhaustive"); true } _ => { self.tcx.sess.emit_err(errors::NonExhaustiveWrongLocation { attr_span: attr.span, defn_span: span, }); false } } } /// Checks if the `#[marker]` attribute on an `item` is valid. Returns `true` if valid. fn check_marker(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) -> bool { match target { Target::Trait => true, // FIXME(#80564): We permit struct fields, match arms and macro defs to have an // `#[marker]` attribute with just a lint, because we previously // erroneously allowed it and some crates used it accidentally, to be compatible // with crates depending on them, we can't throw an error here. Target::Field | Target::Arm | Target::MacroDef => { self.inline_attr_str_error_with_macro_def(hir_id, attr, "marker"); true } _ => { self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToTrait { attr_span: attr.span, defn_span: span, }); false } } } /// Checks if the `#[target_feature]` attribute on `item` is valid. Returns `true` if valid. fn check_target_feature( &self, hir_id: HirId, attr: &Attribute, span: Span, target: Target, attrs: &[Attribute], ) -> bool { match target { Target::Fn => { // `#[target_feature]` is not allowed in language items. if let Some((lang_item, _)) = hir::lang_items::extract(attrs) // Calling functions with `#[target_feature]` is // not unsafe on WASM, see #84988 && !self.tcx.sess.target.is_like_wasm && !self.tcx.sess.opts.actually_rustdoc { let hir::Node::Item(item) = self.tcx.hir().get(hir_id) else { unreachable!(); }; let hir::ItemKind::Fn(sig, _, _) = item.kind else { // target is `Fn` unreachable!(); }; self.tcx.sess.emit_err(errors::LangItemWithTargetFeature { attr_span: attr.span, name: lang_item, sig_span: sig.span, }); false } else { true } } Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true, // FIXME: #[target_feature] was previously erroneously allowed on statements and some // crates used this, so only emit a warning. Target::Statement => { self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::TargetFeatureOnStatement, ); true } // FIXME(#80564): We permit struct fields, match arms and macro defs to have an // `#[target_feature]` attribute with just a lint, because we previously // erroneously allowed it and some crates used it accidentally, to be compatible // with crates depending on them, we can't throw an error here. Target::Field | Target::Arm | Target::MacroDef => { self.inline_attr_str_error_with_macro_def(hir_id, attr, "target_feature"); true } _ => { self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn { attr_span: attr.span, defn_span: span, on_crate: hir_id == CRATE_HIR_ID, }); false } } } /// Checks if the `#[thread_local]` attribute on `item` is valid. Returns `true` if valid. fn check_thread_local(&self, attr: &Attribute, span: Span, target: Target) -> bool { match target { Target::ForeignStatic | Target::Static => true, _ => { self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToStatic { attr_span: attr.span, defn_span: span, }); false } } } fn doc_attr_str_error(&self, meta: &NestedMetaItem, attr_name: &str) { self.tcx.sess.emit_err(errors::DocExpectStr { attr_span: meta.span(), attr_name }); } fn check_doc_alias_value( &self, meta: &NestedMetaItem, doc_alias: Symbol, hir_id: HirId, target: Target, is_list: bool, aliases: &mut FxHashMap, ) -> bool { let tcx = self.tcx; let span = meta.name_value_literal_span().unwrap_or_else(|| meta.span()); let attr_str = &format!("`#[doc(alias{})]`", if is_list { "(\"...\")" } else { " = \"...\"" }); if doc_alias == kw::Empty { tcx.sess.emit_err(errors::DocAliasEmpty { span, attr_str }); return false; } let doc_alias_str = doc_alias.as_str(); if let Some(c) = doc_alias_str .chars() .find(|&c| c == '"' || c == '\'' || (c.is_whitespace() && c != ' ')) { tcx.sess.emit_err(errors::DocAliasBadChar { span, attr_str, char_: c }); return false; } if doc_alias_str.starts_with(' ') || doc_alias_str.ends_with(' ') { tcx.sess.emit_err(errors::DocAliasStartEnd { span, attr_str }); return false; } let span = meta.span(); if let Some(location) = match target { Target::AssocTy => { let parent_def_id = self.tcx.hir().get_parent_item(hir_id).def_id; let containing_item = self.tcx.hir().expect_item(parent_def_id); if Target::from_item(containing_item) == Target::Impl { Some("type alias in implementation block") } else { None } } Target::AssocConst => { let parent_def_id = self.tcx.hir().get_parent_item(hir_id).def_id; let containing_item = self.tcx.hir().expect_item(parent_def_id); // We can't link to trait impl's consts. let err = "associated constant in trait implementation block"; match containing_item.kind { ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) => Some(err), _ => None, } } // we check the validity of params elsewhere Target::Param => return false, Target::Expression | Target::Statement | Target::Arm | Target::ForeignMod | Target::Closure | Target::Impl => Some(target.name()), Target::ExternCrate | Target::Use | Target::Static | Target::Const | Target::Fn | Target::Mod | Target::GlobalAsm | Target::TyAlias | Target::OpaqueTy | Target::Enum | Target::Variant | Target::Struct | Target::Field | Target::Union | Target::Trait | Target::TraitAlias | Target::Method(..) | Target::ForeignFn | Target::ForeignStatic | Target::ForeignTy | Target::GenericParam(..) | Target::MacroDef | Target::PatField | Target::ExprField => None, } { tcx.sess.emit_err(errors::DocAliasBadLocation { span, attr_str, location }); return false; } let item_name = self.tcx.hir().name(hir_id); if item_name == doc_alias { tcx.sess.emit_err(errors::DocAliasNotAnAlias { span, attr_str }); return false; } if let Err(entry) = aliases.try_insert(doc_alias_str.to_owned(), span) { self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, span, errors::DocAliasDuplicated { first_defn: *entry.entry.get() }, ); } true } fn check_doc_alias( &self, meta: &NestedMetaItem, hir_id: HirId, target: Target, aliases: &mut FxHashMap, ) -> bool { if let Some(values) = meta.meta_item_list() { let mut errors = 0; for v in values { match v.lit() { Some(l) => match l.kind { LitKind::Str(s, _) => { if !self.check_doc_alias_value(v, s, hir_id, target, true, aliases) { errors += 1; } } _ => { self.tcx .sess .emit_err(errors::DocAliasNotStringLiteral { span: v.span() }); errors += 1; } }, None => { self.tcx.sess.emit_err(errors::DocAliasNotStringLiteral { span: v.span() }); errors += 1; } } } errors == 0 } else if let Some(doc_alias) = meta.value_str() { self.check_doc_alias_value(meta, doc_alias, hir_id, target, false, aliases) } else { self.tcx.sess.emit_err(errors::DocAliasMalformed { span: meta.span() }); false } } fn check_doc_keyword(&self, meta: &NestedMetaItem, hir_id: HirId) -> bool { let doc_keyword = meta.value_str().unwrap_or(kw::Empty); if doc_keyword == kw::Empty { self.doc_attr_str_error(meta, "keyword"); return false; } match self.tcx.hir().find(hir_id).and_then(|node| match node { hir::Node::Item(item) => Some(&item.kind), _ => None, }) { Some(ItemKind::Mod(ref module)) => { if !module.item_ids.is_empty() { self.tcx.sess.emit_err(errors::DocKeywordEmptyMod { span: meta.span() }); return false; } } _ => { self.tcx.sess.emit_err(errors::DocKeywordNotMod { span: meta.span() }); return false; } } if !rustc_lexer::is_ident(doc_keyword.as_str()) { self.tcx.sess.emit_err(errors::DocKeywordInvalidIdent { span: meta.name_value_literal_span().unwrap_or_else(|| meta.span()), doc_keyword, }); return false; } true } fn check_doc_fake_variadic(&self, meta: &NestedMetaItem, hir_id: HirId) -> bool { match self.tcx.hir().find(hir_id).and_then(|node| match node { hir::Node::Item(item) => Some(&item.kind), _ => None, }) { Some(ItemKind::Impl(ref i)) => { let is_valid = matches!(&i.self_ty.kind, hir::TyKind::Tup([_])) || if let hir::TyKind::BareFn(bare_fn_ty) = &i.self_ty.kind { bare_fn_ty.decl.inputs.len() == 1 } else { false }; if !is_valid { self.tcx.sess.emit_err(errors::DocFakeVariadicNotValid { span: meta.span() }); return false; } } _ => { self.tcx.sess.emit_err(errors::DocKeywordOnlyImpl { span: meta.span() }); return false; } } true } /// Checks `#[doc(inline)]`/`#[doc(no_inline)]` attributes. Returns `true` if valid. /// /// A doc inlining attribute is invalid if it is applied to a non-`use` item, or /// if there are conflicting attributes for one item. /// /// `specified_inline` is used to keep track of whether we have /// already seen an inlining attribute for this item. /// If so, `specified_inline` holds the value and the span of /// the first `inline`/`no_inline` attribute. fn check_doc_inline( &self, attr: &Attribute, meta: &NestedMetaItem, hir_id: HirId, target: Target, specified_inline: &mut Option<(bool, Span)>, ) -> bool { match target { Target::Use | Target::ExternCrate => { let do_inline = meta.name_or_empty() == sym::inline; if let Some((prev_inline, prev_span)) = *specified_inline { if do_inline != prev_inline { let mut spans = MultiSpan::from_spans(vec![prev_span, meta.span()]); spans.push_span_label(prev_span, fluent::passes_doc_inline_conflict_first); spans.push_span_label( meta.span(), fluent::passes_doc_inline_conflict_second, ); self.tcx.sess.emit_err(errors::DocKeywordConflict { spans }); return false; } true } else { *specified_inline = Some((do_inline, meta.span())); true } } _ => { self.tcx.emit_spanned_lint( INVALID_DOC_ATTRIBUTES, hir_id, meta.span(), errors::DocInlineOnlyUse { attr_span: meta.span(), item_span: (attr.style == AttrStyle::Outer) .then(|| self.tcx.hir().span(hir_id)), }, ); false } } } fn check_doc_masked( &self, attr: &Attribute, meta: &NestedMetaItem, hir_id: HirId, target: Target, ) -> bool { if target != Target::ExternCrate { self.tcx.emit_spanned_lint( INVALID_DOC_ATTRIBUTES, hir_id, meta.span(), errors::DocMaskedOnlyExternCrate { attr_span: meta.span(), item_span: (attr.style == AttrStyle::Outer) .then(|| self.tcx.hir().span(hir_id)), }, ); return false; } if self.tcx.extern_mod_stmt_cnum(hir_id.owner).is_none() { self.tcx.emit_spanned_lint( INVALID_DOC_ATTRIBUTES, hir_id, meta.span(), errors::DocMaskedNotExternCrateSelf { attr_span: meta.span(), item_span: (attr.style == AttrStyle::Outer) .then(|| self.tcx.hir().span(hir_id)), }, ); return false; } true } /// Checks that an attribute is *not* used at the crate level. Returns `true` if valid. fn check_attr_not_crate_level( &self, meta: &NestedMetaItem, hir_id: HirId, attr_name: &str, ) -> bool { if CRATE_HIR_ID == hir_id { self.tcx.sess.emit_err(errors::DocAttrNotCrateLevel { span: meta.span(), attr_name }); return false; } true } /// Checks that an attribute is used at the crate level. Returns `true` if valid. fn check_attr_crate_level( &self, attr: &Attribute, meta: &NestedMetaItem, hir_id: HirId, ) -> bool { if hir_id != CRATE_HIR_ID { // insert a bang between `#` and `[...` let bang_span = attr.span.lo() + BytePos(1); let sugg = (attr.style == AttrStyle::Outer && self.tcx.hir().get_parent_item(hir_id) == CRATE_OWNER_ID) .then_some(errors::AttrCrateLevelOnlySugg { attr: attr.span.with_lo(bang_span).with_hi(bang_span), }); self.tcx.emit_spanned_lint( INVALID_DOC_ATTRIBUTES, hir_id, meta.span(), errors::AttrCrateLevelOnly { sugg }, ); return false; } true } /// Checks that `doc(test(...))` attribute contains only valid attributes. Returns `true` if /// valid. fn check_test_attr(&self, meta: &NestedMetaItem, hir_id: HirId) -> bool { let mut is_valid = true; if let Some(metas) = meta.meta_item_list() { for i_meta in metas { match (i_meta.name_or_empty(), i_meta.meta_item()) { (sym::attr | sym::no_crate_inject, _) => {} (_, Some(m)) => { self.tcx.emit_spanned_lint( INVALID_DOC_ATTRIBUTES, hir_id, i_meta.span(), errors::DocTestUnknown { path: rustc_ast_pretty::pprust::path_to_string(&m.path), }, ); is_valid = false; } (_, None) => { self.tcx.emit_spanned_lint( INVALID_DOC_ATTRIBUTES, hir_id, i_meta.span(), errors::DocTestLiteral, ); is_valid = false; } } } } else { self.tcx.emit_spanned_lint( INVALID_DOC_ATTRIBUTES, hir_id, meta.span(), errors::DocTestTakesList, ); is_valid = false; } is_valid } /// Check that the `#![doc(cfg_hide(...))]` attribute only contains a list of attributes. /// Returns `true` if valid. fn check_doc_cfg_hide(&self, meta: &NestedMetaItem, hir_id: HirId) -> bool { if meta.meta_item_list().is_some() { true } else { self.tcx.emit_spanned_lint( INVALID_DOC_ATTRIBUTES, hir_id, meta.span(), errors::DocCfgHideTakesList, ); false } } /// Runs various checks on `#[doc]` attributes. Returns `true` if valid. /// /// `specified_inline` should be initialized to `None` and kept for the scope /// of one item. Read the documentation of [`check_doc_inline`] for more information. /// /// [`check_doc_inline`]: Self::check_doc_inline fn check_doc_attrs( &self, attr: &Attribute, hir_id: HirId, target: Target, specified_inline: &mut Option<(bool, Span)>, aliases: &mut FxHashMap, ) -> bool { let mut is_valid = true; if let Some(mi) = attr.meta() && let Some(list) = mi.meta_item_list() { for meta in list { if let Some(i_meta) = meta.meta_item() { match i_meta.name_or_empty() { sym::alias if !self.check_attr_not_crate_level(meta, hir_id, "alias") || !self.check_doc_alias(meta, hir_id, target, aliases) => { is_valid = false } sym::keyword if !self.check_attr_not_crate_level(meta, hir_id, "keyword") || !self.check_doc_keyword(meta, hir_id) => { is_valid = false } sym::fake_variadic if !self.check_attr_not_crate_level(meta, hir_id, "fake_variadic") || !self.check_doc_fake_variadic(meta, hir_id) => { is_valid = false } sym::html_favicon_url | sym::html_logo_url | sym::html_playground_url | sym::issue_tracker_base_url | sym::html_root_url | sym::html_no_source | sym::test | sym::rust_logo if !self.check_attr_crate_level(attr, meta, hir_id) => { is_valid = false; } sym::cfg_hide if !self.check_attr_crate_level(attr, meta, hir_id) || !self.check_doc_cfg_hide(meta, hir_id) => { is_valid = false; } sym::inline | sym::no_inline if !self.check_doc_inline( attr, meta, hir_id, target, specified_inline, ) => { is_valid = false; } sym::masked if !self.check_doc_masked(attr, meta, hir_id, target) => { is_valid = false; } // no_default_passes: deprecated // passes: deprecated // plugins: removed, but rustdoc warns about it itself sym::alias | sym::cfg | sym::cfg_hide | sym::hidden | sym::html_favicon_url | sym::html_logo_url | sym::html_no_source | sym::html_playground_url | sym::html_root_url | sym::inline | sym::issue_tracker_base_url | sym::keyword | sym::masked | sym::no_default_passes | sym::no_inline | sym::notable_trait | sym::passes | sym::plugins | sym::fake_variadic => {} sym::rust_logo => { if !self.tcx.features().rustdoc_internals { feature_err( &self.tcx.sess.parse_sess, sym::rustdoc_internals, meta.span(), "the `#[doc(rust_logo)]` attribute is used for Rust branding", ) .emit(); } } sym::test => { if !self.check_test_attr(meta, hir_id) { is_valid = false; } } _ => { let path = rustc_ast_pretty::pprust::path_to_string(&i_meta.path); if i_meta.has_name(sym::spotlight) { self.tcx.emit_spanned_lint( INVALID_DOC_ATTRIBUTES, hir_id, i_meta.span, errors::DocTestUnknownSpotlight { path, span: i_meta.span }, ); } else if i_meta.has_name(sym::include) && let Some(value) = i_meta.value_str() { let applicability = if list.len() == 1 { Applicability::MachineApplicable } else { Applicability::MaybeIncorrect }; // If there are multiple attributes, the suggestion would suggest // deleting all of them, which is incorrect. self.tcx.emit_spanned_lint( INVALID_DOC_ATTRIBUTES, hir_id, i_meta.span, errors::DocTestUnknownInclude { path, value: value.to_string(), inner: match attr.style { AttrStyle::Inner => "!", AttrStyle::Outer => "", }, sugg: (attr.meta().unwrap().span, applicability), }, ); } else { self.tcx.emit_spanned_lint( INVALID_DOC_ATTRIBUTES, hir_id, i_meta.span, errors::DocTestUnknownAny { path }, ); } is_valid = false; } } } else { self.tcx.emit_spanned_lint( INVALID_DOC_ATTRIBUTES, hir_id, meta.span(), errors::DocInvalid, ); is_valid = false; } } } is_valid } /// Warns against some misuses of `#[pass_by_value]` fn check_pass_by_value(&self, attr: &Attribute, span: Span, target: Target) -> bool { match target { Target::Struct | Target::Enum | Target::TyAlias => true, _ => { self.tcx.sess.emit_err(errors::PassByValue { attr_span: attr.span, span }); false } } } fn check_allow_incoherent_impl(&self, attr: &Attribute, span: Span, target: Target) -> bool { match target { Target::Method(MethodKind::Inherent) => true, _ => { self.tcx.sess.emit_err(errors::AllowIncoherentImpl { attr_span: attr.span, span }); false } } } fn check_has_incoherent_inherent_impls( &self, attr: &Attribute, span: Span, target: Target, ) -> bool { match target { Target::Trait | Target::Struct | Target::Enum | Target::Union | Target::ForeignTy => { true } _ => { self.tcx .sess .emit_err(errors::HasIncoherentInherentImpl { attr_span: attr.span, span }); false } } } fn check_ffi_pure(&self, attr_span: Span, attrs: &[Attribute], target: Target) -> bool { if target != Target::ForeignFn { self.tcx.sess.emit_err(errors::FfiPureInvalidTarget { attr_span }); return false; } if attrs.iter().any(|a| a.has_name(sym::ffi_const)) { // `#[ffi_const]` functions cannot be `#[ffi_pure]` self.tcx.sess.emit_err(errors::BothFfiConstAndPure { attr_span }); false } else { true } } fn check_ffi_const(&self, attr_span: Span, target: Target) -> bool { if target == Target::ForeignFn { true } else { self.tcx.sess.emit_err(errors::FfiConstInvalidTarget { attr_span }); false } } fn check_ffi_returns_twice(&self, attr_span: Span, target: Target) -> bool { if target == Target::ForeignFn { true } else { self.tcx.sess.emit_err(errors::FfiReturnsTwiceInvalidTarget { attr_span }); false } } /// Warns against some misuses of `#[must_use]` fn check_must_use(&self, hir_id: HirId, attr: &Attribute, target: Target) -> bool { if !matches!( target, Target::Fn | Target::Enum | Target::Struct | Target::Union | Target::Method(_) | Target::ForeignFn // `impl Trait` in return position can trip // `unused_must_use` if `Trait` is marked as // `#[must_use]` | Target::Trait ) { let article = match target { Target::ExternCrate | Target::OpaqueTy | Target::Enum | Target::Impl | Target::Expression | Target::Arm | Target::AssocConst | Target::AssocTy => "an", _ => "a", }; self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::MustUseNoEffect { article, target }, ); } // For now, its always valid true } /// Checks if `#[must_not_suspend]` is applied to a function. Returns `true` if valid. fn check_must_not_suspend(&self, attr: &Attribute, span: Span, target: Target) -> bool { match target { Target::Struct | Target::Enum | Target::Union | Target::Trait => true, _ => { self.tcx.sess.emit_err(errors::MustNotSuspend { attr_span: attr.span, span }); false } } } /// Checks if `#[cold]` is applied to a non-function. Returns `true` if valid. fn check_cold(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) { match target { Target::Fn | Target::Method(..) | Target::ForeignFn | Target::Closure => {} // FIXME(#80564): We permit struct fields, match arms and macro defs to have an // `#[cold]` attribute with just a lint, because we previously // erroneously allowed it and some crates used it accidentally, to be compatible // with crates depending on them, we can't throw an error here. Target::Field | Target::Arm | Target::MacroDef => { self.inline_attr_str_error_with_macro_def(hir_id, attr, "cold"); } _ => { // FIXME: #[cold] was previously allowed on non-functions and some crates used // this, so only emit a warning. self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::Cold { span, on_crate: hir_id == CRATE_HIR_ID }, ); } } } /// Checks if `#[link]` is applied to an item other than a foreign module. fn check_link(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) { if target == Target::ForeignMod && let hir::Node::Item(item) = self.tcx.hir().get(hir_id) && let Item { kind: ItemKind::ForeignMod { abi, .. }, .. } = item && !matches!(abi, Abi::Rust | Abi::RustIntrinsic | Abi::PlatformIntrinsic) { return; } self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::Link { span: (target != Target::ForeignMod).then_some(span) }, ); } /// Checks if `#[link_name]` is applied to an item other than a foreign function or static. fn check_link_name(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) { match target { Target::ForeignFn | Target::ForeignStatic => {} // FIXME(#80564): We permit struct fields, match arms and macro defs to have an // `#[link_name]` attribute with just a lint, because we previously // erroneously allowed it and some crates used it accidentally, to be compatible // with crates depending on them, we can't throw an error here. Target::Field | Target::Arm | Target::MacroDef => { self.inline_attr_str_error_with_macro_def(hir_id, attr, "link_name"); } _ => { // FIXME: #[cold] was previously allowed on non-functions/statics and some crates // used this, so only emit a warning. let attr_span = matches!(target, Target::ForeignMod).then_some(attr.span); if let Some(s) = attr.value_str() { self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::LinkName { span, attr_span, value: s.as_str() }, ); } else { self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::LinkName { span, attr_span, value: "..." }, ); }; } } } /// Checks if `#[no_link]` is applied to an `extern crate`. Returns `true` if valid. fn check_no_link(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) -> bool { match target { Target::ExternCrate => true, // FIXME(#80564): We permit struct fields, match arms and macro defs to have an // `#[no_link]` attribute with just a lint, because we previously // erroneously allowed it and some crates used it accidentally, to be compatible // with crates depending on them, we can't throw an error here. Target::Field | Target::Arm | Target::MacroDef => { self.inline_attr_str_error_with_macro_def(hir_id, attr, "no_link"); true } _ => { self.tcx.sess.emit_err(errors::NoLink { attr_span: attr.span, span }); false } } } fn is_impl_item(&self, hir_id: HirId) -> bool { matches!(self.tcx.hir().get(hir_id), hir::Node::ImplItem(..)) } /// Checks if `#[export_name]` is applied to a function or static. Returns `true` if valid. fn check_export_name( &self, hir_id: HirId, attr: &Attribute, span: Span, target: Target, ) -> bool { match target { Target::Static | Target::Fn => true, Target::Method(..) if self.is_impl_item(hir_id) => true, // FIXME(#80564): We permit struct fields, match arms and macro defs to have an // `#[export_name]` attribute with just a lint, because we previously // erroneously allowed it and some crates used it accidentally, to be compatible // with crates depending on them, we can't throw an error here. Target::Field | Target::Arm | Target::MacroDef => { self.inline_attr_str_error_with_macro_def(hir_id, attr, "export_name"); true } _ => { self.tcx.sess.emit_err(errors::ExportName { attr_span: attr.span, span }); false } } } fn check_rustc_layout_scalar_valid_range( &self, attr: &Attribute, span: Span, target: Target, ) -> bool { if target != Target::Struct { self.tcx.sess.emit_err(errors::RustcLayoutScalarValidRangeNotStruct { attr_span: attr.span, span, }); return false; } let Some(list) = attr.meta_item_list() else { return false; }; if matches!(&list[..], &[NestedMetaItem::Lit(MetaItemLit { kind: LitKind::Int(..), .. })]) { true } else { self.tcx.sess.emit_err(errors::RustcLayoutScalarValidRangeArg { attr_span: attr.span }); false } } /// Checks if `#[rustc_legacy_const_generics]` is applied to a function and has a valid argument. fn check_rustc_legacy_const_generics( &self, hir_id: HirId, attr: &Attribute, span: Span, target: Target, item: Option>, ) -> bool { let is_function = matches!(target, Target::Fn); if !is_function { self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn { attr_span: attr.span, defn_span: span, on_crate: hir_id == CRATE_HIR_ID, }); return false; } let Some(list) = attr.meta_item_list() else { // The attribute form is validated on AST. return false; }; let Some(ItemLike::Item(Item { kind: ItemKind::Fn(FnSig { decl, .. }, generics, _), .. })) = item else { bug!("should be a function item"); }; for param in generics.params { match param.kind { hir::GenericParamKind::Const { .. } => {} _ => { self.tcx.sess.emit_err(errors::RustcLegacyConstGenericsOnly { attr_span: attr.span, param_span: param.span, }); return false; } } } if list.len() != generics.params.len() { self.tcx.sess.emit_err(errors::RustcLegacyConstGenericsIndex { attr_span: attr.span, generics_span: generics.span, }); return false; } let arg_count = decl.inputs.len() as u128 + generics.params.len() as u128; let mut invalid_args = vec![]; for meta in list { if let Some(LitKind::Int(val, _)) = meta.lit().map(|lit| &lit.kind) { if *val >= arg_count { let span = meta.span(); self.tcx.sess.emit_err(errors::RustcLegacyConstGenericsIndexExceed { span, arg_count: arg_count as usize, }); return false; } } else { invalid_args.push(meta.span()); } } if !invalid_args.is_empty() { self.tcx.sess.emit_err(errors::RustcLegacyConstGenericsIndexNegative { invalid_args }); false } else { true } } /// Helper function for checking that the provided attribute is only applied to a function or /// method. fn check_applied_to_fn_or_method( &self, hir_id: HirId, attr: &Attribute, span: Span, target: Target, ) -> bool { let is_function = matches!(target, Target::Fn | Target::Method(..)); if !is_function { self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn { attr_span: attr.span, defn_span: span, on_crate: hir_id == CRATE_HIR_ID, }); false } else { true } } /// Checks that the `#[rustc_lint_query_instability]` attribute is only applied to a function /// or method. fn check_rustc_lint_query_instability( &self, hir_id: HirId, attr: &Attribute, span: Span, target: Target, ) -> bool { self.check_applied_to_fn_or_method(hir_id, attr, span, target) } /// Checks that the `#[rustc_lint_diagnostics]` attribute is only applied to a function or /// method. fn check_rustc_lint_diagnostics( &self, hir_id: HirId, attr: &Attribute, span: Span, target: Target, ) -> bool { self.check_applied_to_fn_or_method(hir_id, attr, span, target) } /// Checks that the `#[rustc_lint_opt_ty]` attribute is only applied to a struct. fn check_rustc_lint_opt_ty(&self, attr: &Attribute, span: Span, target: Target) -> bool { match target { Target::Struct => true, _ => { self.tcx.sess.emit_err(errors::RustcLintOptTy { attr_span: attr.span, span }); false } } } /// Checks that the `#[rustc_lint_opt_deny_field_access]` attribute is only applied to a field. fn check_rustc_lint_opt_deny_field_access( &self, attr: &Attribute, span: Span, target: Target, ) -> bool { match target { Target::Field => true, _ => { self.tcx .sess .emit_err(errors::RustcLintOptDenyFieldAccess { attr_span: attr.span, span }); false } } } /// Checks that the dep-graph debugging attributes are only present when the query-dep-graph /// option is passed to the compiler. fn check_rustc_dirty_clean(&self, attr: &Attribute) -> bool { if self.tcx.sess.opts.unstable_opts.query_dep_graph { true } else { self.tcx.sess.emit_err(errors::RustcDirtyClean { span: attr.span }); false } } /// Checks if the attribute is applied to a trait. fn check_must_be_applied_to_trait(&self, attr: &Attribute, span: Span, target: Target) -> bool { match target { Target::Trait => true, _ => { self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToTrait { attr_span: attr.span, defn_span: span, }); false } } } /// Checks if `#[link_section]` is applied to a function or static. fn check_link_section(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) { match target { Target::Static | Target::Fn | Target::Method(..) => {} // FIXME(#80564): We permit struct fields, match arms and macro defs to have an // `#[link_section]` attribute with just a lint, because we previously // erroneously allowed it and some crates used it accidentally, to be compatible // with crates depending on them, we can't throw an error here. Target::Field | Target::Arm | Target::MacroDef => { self.inline_attr_str_error_with_macro_def(hir_id, attr, "link_section"); } _ => { // FIXME: #[link_section] was previously allowed on non-functions/statics and some // crates used this, so only emit a warning. self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::LinkSection { span }, ); } } } /// Checks if `#[no_mangle]` is applied to a function or static. fn check_no_mangle(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) { match target { Target::Static | Target::Fn => {} Target::Method(..) if self.is_impl_item(hir_id) => {} // FIXME(#80564): We permit struct fields, match arms and macro defs to have an // `#[no_mangle]` attribute with just a lint, because we previously // erroneously allowed it and some crates used it accidentally, to be compatible // with crates depending on them, we can't throw an error here. Target::Field | Target::Arm | Target::MacroDef => { self.inline_attr_str_error_with_macro_def(hir_id, attr, "no_mangle"); } // FIXME: #[no_mangle] was previously allowed on non-functions/statics, this should be an error // The error should specify that the item that is wrong is specifically a *foreign* fn/static // otherwise the error seems odd Target::ForeignFn | Target::ForeignStatic => { let foreign_item_kind = match target { Target::ForeignFn => "function", Target::ForeignStatic => "static", _ => unreachable!(), }; self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::NoMangleForeign { span, attr_span: attr.span, foreign_item_kind }, ); } _ => { // FIXME: #[no_mangle] was previously allowed on non-functions/statics and some // crates used this, so only emit a warning. self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::NoMangle { span }, ); } } } /// Checks if the `#[repr]` attributes on `item` are valid. fn check_repr( &self, attrs: &[Attribute], span: Span, target: Target, item: Option>, hir_id: HirId, ) { // Extract the names of all repr hints, e.g., [foo, bar, align] for: // ``` // #[repr(foo)] // #[repr(bar, align(8))] // ``` let hints: Vec<_> = attrs .iter() .filter(|attr| attr.has_name(sym::repr)) .filter_map(|attr| attr.meta_item_list()) .flatten() .collect(); let mut int_reprs = 0; let mut is_explicit_rust = false; let mut is_c = false; let mut is_simd = false; let mut is_transparent = false; for hint in &hints { if !hint.is_meta_item() { self.tcx.sess.emit_err(errors::ReprIdent { span: hint.span() }); continue; } match hint.name_or_empty() { sym::Rust => { is_explicit_rust = true; } sym::C => { is_c = true; match target { Target::Struct | Target::Union | Target::Enum => continue, _ => { self.tcx.sess.emit_err(errors::AttrApplication::StructEnumUnion { hint_span: hint.span(), span, }); } } } sym::align => { if let (Target::Fn | Target::Method(MethodKind::Inherent), false) = (target, self.tcx.features().fn_align) { feature_err( &self.tcx.sess.parse_sess, sym::fn_align, hint.span(), "`repr(align)` attributes on functions are unstable", ) .emit(); } match target { Target::Struct | Target::Union | Target::Enum | Target::Fn | Target::Method(_) => continue, _ => { self.tcx.sess.emit_err( errors::AttrApplication::StructEnumFunctionMethodUnion { hint_span: hint.span(), span, }, ); } } } sym::packed => { if target != Target::Struct && target != Target::Union { self.tcx.sess.emit_err(errors::AttrApplication::StructUnion { hint_span: hint.span(), span, }); } else { continue; } } sym::simd => { is_simd = true; if target != Target::Struct { self.tcx.sess.emit_err(errors::AttrApplication::Struct { hint_span: hint.span(), span, }); } else { continue; } } sym::transparent => { is_transparent = true; match target { Target::Struct | Target::Union | Target::Enum => continue, _ => { self.tcx.sess.emit_err(errors::AttrApplication::StructEnumUnion { hint_span: hint.span(), span, }); } } } sym::i8 | sym::u8 | sym::i16 | sym::u16 | sym::i32 | sym::u32 | sym::i64 | sym::u64 | sym::i128 | sym::u128 | sym::isize | sym::usize => { int_reprs += 1; if target != Target::Enum { self.tcx.sess.emit_err(errors::AttrApplication::Enum { hint_span: hint.span(), span, }); } else { continue; } } _ => { self.tcx.sess.emit_err(errors::UnrecognizedReprHint { span: hint.span() }); continue; } }; } // Just point at all repr hints if there are any incompatibilities. // This is not ideal, but tracking precisely which ones are at fault is a huge hassle. let hint_spans = hints.iter().map(|hint| hint.span()); // Error on repr(transparent, ). if is_transparent && hints.len() > 1 { let hint_spans = hint_spans.clone().collect(); self.tcx.sess.emit_err(errors::TransparentIncompatible { hint_spans, target: target.to_string(), }); } if is_explicit_rust && (int_reprs > 0 || is_c || is_simd) { let hint_spans = hint_spans.clone().collect(); self.tcx.sess.emit_err(errors::ReprConflicting { hint_spans }); } // Warn on repr(u8, u16), repr(C, simd), and c-like-enum-repr(C, u8) if (int_reprs > 1) || (is_simd && is_c) || (int_reprs == 1 && is_c && item.is_some_and(|item| { if let ItemLike::Item(item) = item { return is_c_like_enum(item); } return false; })) { self.tcx.emit_spanned_lint( CONFLICTING_REPR_HINTS, hir_id, hint_spans.collect::>(), errors::ReprConflictingLint, ); } } fn check_used(&self, attrs: &[Attribute], target: Target) { let mut used_linker_span = None; let mut used_compiler_span = None; for attr in attrs.iter().filter(|attr| attr.has_name(sym::used)) { if target != Target::Static { self.tcx.sess.emit_err(errors::UsedStatic { span: attr.span }); } let inner = attr.meta_item_list(); match inner.as_deref() { Some([item]) if item.has_name(sym::linker) => { if used_linker_span.is_none() { used_linker_span = Some(attr.span); } } Some([item]) if item.has_name(sym::compiler) => { if used_compiler_span.is_none() { used_compiler_span = Some(attr.span); } } Some(_) => { // This error case is handled in rustc_hir_analysis::collect. } None => { // Default case (compiler) when arg isn't defined. if used_compiler_span.is_none() { used_compiler_span = Some(attr.span); } } } } if let (Some(linker_span), Some(compiler_span)) = (used_linker_span, used_compiler_span) { self.tcx .sess .emit_err(errors::UsedCompilerLinker { spans: vec![linker_span, compiler_span] }); } } /// Outputs an error for `#[allow_internal_unstable]` which can only be applied to macros. /// (Allows proc_macro functions) fn check_allow_internal_unstable( &self, hir_id: HirId, attr: &Attribute, span: Span, target: Target, attrs: &[Attribute], ) -> bool { debug!("Checking target: {:?}", target); match target { Target::Fn => { for attr in attrs { if attr.is_proc_macro_attr() { debug!("Is proc macro attr"); return true; } } debug!("Is not proc macro attr"); false } Target::MacroDef => true, // FIXME(#80564): We permit struct fields and match arms to have an // `#[allow_internal_unstable]` attribute with just a lint, because we previously // erroneously allowed it and some crates used it accidentally, to be compatible // with crates depending on them, we can't throw an error here. Target::Field | Target::Arm => { self.inline_attr_str_error_without_macro_def( hir_id, attr, "allow_internal_unstable", ); true } _ => { self.tcx .sess .emit_err(errors::AllowInternalUnstable { attr_span: attr.span, span }); false } } } /// Checks if the items on the `#[debugger_visualizer]` attribute are valid. fn check_debugger_visualizer(&self, attr: &Attribute, target: Target) -> bool { // Here we only check that the #[debugger_visualizer] attribute is attached // to nothing other than a module. All other checks are done in the // `debugger_visualizer` query where they need to be done for decoding // anyway. match target { Target::Mod => {} _ => { self.tcx.sess.emit_err(errors::DebugVisualizerPlacement { span: attr.span }); return false; } } true } /// Outputs an error for `#[allow_internal_unstable]` which can only be applied to macros. /// (Allows proc_macro functions) fn check_rustc_allow_const_fn_unstable( &self, hir_id: HirId, attr: &Attribute, span: Span, target: Target, ) -> bool { match target { Target::Fn | Target::Method(_) if self.tcx.is_const_fn_raw(hir_id.expect_owner().to_def_id()) => { true } // FIXME(#80564): We permit struct fields and match arms to have an // `#[allow_internal_unstable]` attribute with just a lint, because we previously // erroneously allowed it and some crates used it accidentally, to be compatible // with crates depending on them, we can't throw an error here. Target::Field | Target::Arm | Target::MacroDef => { self.inline_attr_str_error_with_macro_def(hir_id, attr, "allow_internal_unstable"); true } _ => { self.tcx .sess .emit_err(errors::RustcAllowConstFnUnstable { attr_span: attr.span, span }); false } } } fn check_rustc_safe_intrinsic( &self, hir_id: HirId, attr: &Attribute, span: Span, target: Target, ) -> bool { let hir = self.tcx.hir(); if let Target::ForeignFn = target && let Some(parent) = hir.opt_parent_id(hir_id) && let hir::Node::Item(Item { kind: ItemKind::ForeignMod { abi: Abi::RustIntrinsic | Abi::PlatformIntrinsic, .. }, .. }) = hir.get(parent) { return true; } self.tcx.sess.emit_err(errors::RustcSafeIntrinsic { attr_span: attr.span, span }); false } fn check_rustc_std_internal_symbol( &self, attr: &Attribute, span: Span, target: Target, ) -> bool { match target { Target::Fn | Target::Static => true, _ => { self.tcx .sess .emit_err(errors::RustcStdInternalSymbol { attr_span: attr.span, span }); false } } } fn check_stability_promotable(&self, attr: &Attribute, _span: Span, target: Target) -> bool { match target { Target::Expression => { self.tcx.sess.emit_err(errors::StabilityPromotable { attr_span: attr.span }); false } _ => true, } } fn check_link_ordinal(&self, attr: &Attribute, _span: Span, target: Target) -> bool { match target { Target::ForeignFn | Target::ForeignStatic => true, _ => { self.tcx.sess.emit_err(errors::LinkOrdinal { attr_span: attr.span }); false } } } fn check_confusables(&self, attr: &Attribute, target: Target) -> bool { match target { Target::Method(MethodKind::Inherent) => { let Some(meta) = attr.meta() else { return false; }; let ast::MetaItem { kind: MetaItemKind::List(ref metas), .. } = meta else { return false; }; let mut candidates = Vec::new(); for meta in metas { let NestedMetaItem::Lit(meta_lit) = meta else { self.tcx.sess.emit_err(errors::IncorrectMetaItem { span: meta.span(), suggestion: errors::IncorrectMetaItemSuggestion { lo: meta.span().shrink_to_lo(), hi: meta.span().shrink_to_hi(), }, }); return false; }; candidates.push(meta_lit.symbol); } if candidates.is_empty() { self.tcx.sess.emit_err(errors::EmptyConfusables { span: attr.span }); return false; } true } _ => { self.tcx.sess.emit_err(errors::Confusables { attr_span: attr.span }); false } } } fn check_deprecated(&self, hir_id: HirId, attr: &Attribute, _span: Span, target: Target) { match target { Target::Closure | Target::Expression | Target::Statement | Target::Arm => { self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::Deprecated, ); } _ => {} } } fn check_macro_use(&self, hir_id: HirId, attr: &Attribute, target: Target) { let name = attr.name_or_empty(); match target { Target::ExternCrate | Target::Mod => {} _ => { self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::MacroUse { name }, ); } } } fn check_macro_export(&self, hir_id: HirId, attr: &Attribute, target: Target) { if target != Target::MacroDef { self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::MacroExport::Normal, ); } else if let Some(meta_item_list) = attr.meta_item_list() && !meta_item_list.is_empty() { if meta_item_list.len() > 1 { self.tcx.emit_spanned_lint( INVALID_MACRO_EXPORT_ARGUMENTS, hir_id, attr.span, errors::MacroExport::TooManyItems, ); } else { if meta_item_list[0].name_or_empty() != sym::local_inner_macros { self.tcx.emit_spanned_lint( INVALID_MACRO_EXPORT_ARGUMENTS, hir_id, meta_item_list[0].span(), errors::MacroExport::UnknownItem { name: meta_item_list[0].name_or_empty(), }, ); } } } else { // special case when `#[macro_export]` is applied to a macro 2.0 let (macro_definition, _) = self.tcx.hir().find(hir_id).unwrap().expect_item().expect_macro(); let is_decl_macro = !macro_definition.macro_rules; if is_decl_macro { self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::MacroExport::OnDeclMacro, ); } } } fn check_unused_attribute(&self, hir_id: HirId, attr: &Attribute) { // Warn on useless empty attributes. let note = if matches!( attr.name_or_empty(), sym::macro_use | sym::allow | sym::expect | sym::warn | sym::deny | sym::forbid | sym::feature | sym::repr | sym::target_feature ) && attr.meta_item_list().is_some_and(|list| list.is_empty()) { errors::UnusedNote::EmptyList { name: attr.name_or_empty() } } else if matches!( attr.name_or_empty(), sym::allow | sym::warn | sym::deny | sym::forbid | sym::expect ) && let Some(meta) = attr.meta_item_list() && meta.len() == 1 && let Some(item) = meta[0].meta_item() && let MetaItemKind::NameValue(_) = &item.kind && item.path == sym::reason { errors::UnusedNote::NoLints { name: attr.name_or_empty() } } else if attr.name_or_empty() == sym::default_method_body_is_const { errors::UnusedNote::DefaultMethodBodyConst } else { return; }; self.tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, attr.span, errors::Unused { attr_span: attr.span, note }, ); } /// A best effort attempt to create an error for a mismatching proc macro signature. /// /// If this best effort goes wrong, it will just emit a worse error later (see #102923) fn check_proc_macro(&self, hir_id: HirId, target: Target, kind: ProcMacroKind) { if target != Target::Fn { return; } let tcx = self.tcx; let Some(token_stream_def_id) = tcx.get_diagnostic_item(sym::TokenStream) else { return; }; let Some(token_stream) = tcx.type_of(token_stream_def_id).no_bound_vars() else { return; }; let def_id = hir_id.expect_owner().def_id; let param_env = ty::ParamEnv::empty(); let infcx = tcx.infer_ctxt().build(); let ocx = ObligationCtxt::new(&infcx); let span = tcx.def_span(def_id); let fresh_args = infcx.fresh_args_for_item(span, def_id.to_def_id()); let sig = tcx.liberate_late_bound_regions( def_id.to_def_id(), tcx.fn_sig(def_id).instantiate(tcx, fresh_args), ); let mut cause = ObligationCause::misc(span, def_id); let sig = ocx.normalize(&cause, param_env, sig); // proc macro is not WF. let errors = ocx.select_where_possible(); if !errors.is_empty() { return; } let expected_sig = tcx.mk_fn_sig( std::iter::repeat(token_stream).take(match kind { ProcMacroKind::Attribute => 2, ProcMacroKind::Derive | ProcMacroKind::FunctionLike => 1, }), token_stream, false, Unsafety::Normal, Abi::Rust, ); if let Err(terr) = ocx.eq(&cause, param_env, expected_sig, sig) { let mut diag = tcx.sess.create_err(errors::ProcMacroBadSig { span, kind }); let hir_sig = tcx.hir().fn_sig_by_hir_id(hir_id); if let Some(hir_sig) = hir_sig { match terr { TypeError::ArgumentMutability(idx) | TypeError::ArgumentSorts(_, idx) => { if let Some(ty) = hir_sig.decl.inputs.get(idx) { diag.set_span(ty.span); cause.span = ty.span; } else if idx == hir_sig.decl.inputs.len() { let span = hir_sig.decl.output.span(); diag.set_span(span); cause.span = span; } } TypeError::ArgCount => { if let Some(ty) = hir_sig.decl.inputs.get(expected_sig.inputs().len()) { diag.set_span(ty.span); cause.span = ty.span; } } TypeError::UnsafetyMismatch(_) => { // FIXME: Would be nice if we had a span here.. } TypeError::AbiMismatch(_) => { // FIXME: Would be nice if we had a span here.. } TypeError::VariadicMismatch(_) => { // FIXME: Would be nice if we had a span here.. } _ => {} } } infcx.err_ctxt().note_type_err( &mut diag, &cause, None, Some(ValuePairs::PolySigs(ExpectedFound { expected: ty::Binder::dummy(expected_sig), found: ty::Binder::dummy(sig), })), terr, false, false, ); diag.emit(); self.abort.set(true); } let errors = ocx.select_all_or_error(); if !errors.is_empty() { infcx.err_ctxt().report_fulfillment_errors(errors); self.abort.set(true); } } } impl<'tcx> Visitor<'tcx> for CheckAttrVisitor<'tcx> { type NestedFilter = nested_filter::OnlyBodies; fn nested_visit_map(&mut self) -> Self::Map { self.tcx.hir() } fn visit_item(&mut self, item: &'tcx Item<'tcx>) { // Historically we've run more checks on non-exported than exported macros, // so this lets us continue to run them while maintaining backwards compatibility. // In the long run, the checks should be harmonized. if let ItemKind::Macro(ref macro_def, _) = item.kind { let def_id = item.owner_id.to_def_id(); if macro_def.macro_rules && !self.tcx.has_attr(def_id, sym::macro_export) { check_non_exported_macro_for_invalid_attrs(self.tcx, item); } } let target = Target::from_item(item); self.check_attributes(item.hir_id(), item.span, target, Some(ItemLike::Item(item))); intravisit::walk_item(self, item) } fn visit_generic_param(&mut self, generic_param: &'tcx hir::GenericParam<'tcx>) { let target = Target::from_generic_param(generic_param); self.check_attributes(generic_param.hir_id, generic_param.span, target, None); intravisit::walk_generic_param(self, generic_param) } fn visit_trait_item(&mut self, trait_item: &'tcx TraitItem<'tcx>) { let target = Target::from_trait_item(trait_item); self.check_attributes(trait_item.hir_id(), trait_item.span, target, None); intravisit::walk_trait_item(self, trait_item) } fn visit_field_def(&mut self, struct_field: &'tcx hir::FieldDef<'tcx>) { self.check_attributes(struct_field.hir_id, struct_field.span, Target::Field, None); intravisit::walk_field_def(self, struct_field); } fn visit_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) { self.check_attributes(arm.hir_id, arm.span, Target::Arm, None); intravisit::walk_arm(self, arm); } fn visit_foreign_item(&mut self, f_item: &'tcx ForeignItem<'tcx>) { let target = Target::from_foreign_item(f_item); self.check_attributes(f_item.hir_id(), f_item.span, target, Some(ItemLike::ForeignItem)); intravisit::walk_foreign_item(self, f_item) } fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) { let target = target_from_impl_item(self.tcx, impl_item); self.check_attributes(impl_item.hir_id(), impl_item.span, target, None); intravisit::walk_impl_item(self, impl_item) } fn visit_stmt(&mut self, stmt: &'tcx hir::Stmt<'tcx>) { // When checking statements ignore expressions, they will be checked later. if let hir::StmtKind::Local(ref l) = stmt.kind { self.check_attributes(l.hir_id, stmt.span, Target::Statement, None); } intravisit::walk_stmt(self, stmt) } fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) { let target = match expr.kind { hir::ExprKind::Closure { .. } => Target::Closure, _ => Target::Expression, }; self.check_attributes(expr.hir_id, expr.span, target, None); intravisit::walk_expr(self, expr) } fn visit_expr_field(&mut self, field: &'tcx hir::ExprField<'tcx>) { self.check_attributes(field.hir_id, field.span, Target::ExprField, None); intravisit::walk_expr_field(self, field) } fn visit_variant(&mut self, variant: &'tcx hir::Variant<'tcx>) { self.check_attributes(variant.hir_id, variant.span, Target::Variant, None); intravisit::walk_variant(self, variant) } fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) { self.check_attributes(param.hir_id, param.span, Target::Param, None); intravisit::walk_param(self, param); } fn visit_pat_field(&mut self, field: &'tcx hir::PatField<'tcx>) { self.check_attributes(field.hir_id, field.span, Target::PatField, None); intravisit::walk_pat_field(self, field); } } fn is_c_like_enum(item: &Item<'_>) -> bool { if let ItemKind::Enum(ref def, _) = item.kind { for variant in def.variants { match variant.data { hir::VariantData::Unit(..) => { /* continue */ } _ => return false, } } true } else { false } } // FIXME: Fix "Cannot determine resolution" error and remove built-in macros // from this check. fn check_invalid_crate_level_attr(tcx: TyCtxt<'_>, attrs: &[Attribute]) { // Check for builtin attributes at the crate level // which were unsuccessfully resolved due to cannot determine // resolution for the attribute macro error. const ATTRS_TO_CHECK: &[Symbol] = &[ sym::macro_export, sym::repr, sym::path, sym::automatically_derived, sym::start, sym::rustc_main, sym::unix_sigpipe, sym::derive, sym::test, sym::test_case, sym::global_allocator, sym::bench, ]; for attr in attrs { // This function should only be called with crate attributes // which are inner attributes always but lets check to make sure if attr.style == AttrStyle::Inner { for attr_to_check in ATTRS_TO_CHECK { if attr.has_name(*attr_to_check) { let item = tcx .hir() .items() .map(|id| tcx.hir().item(id)) .find(|item| !item.span.is_dummy()) // Skip prelude `use`s .map(|item| errors::ItemFollowingInnerAttr { span: item.ident.span, kind: item.kind.descr(), }); tcx.sess.emit_err(errors::InvalidAttrAtCrateLevel { span: attr.span, sugg_span: tcx .sess .source_map() .span_to_snippet(attr.span) .ok() .filter(|src| src.starts_with("#![")) .map(|_| { attr.span .with_lo(attr.span.lo() + BytePos(1)) .with_hi(attr.span.lo() + BytePos(2)) }), name: *attr_to_check, item, }); } } } } } fn check_non_exported_macro_for_invalid_attrs(tcx: TyCtxt<'_>, item: &Item<'_>) { let attrs = tcx.hir().attrs(item.hir_id()); for attr in attrs { if attr.has_name(sym::inline) { tcx.sess.emit_err(errors::NonExportedMacroInvalidAttrs { attr_span: attr.span }); } } } fn check_mod_attrs(tcx: TyCtxt<'_>, module_def_id: LocalModDefId) { let check_attr_visitor = &mut CheckAttrVisitor { tcx, abort: Cell::new(false) }; tcx.hir().visit_item_likes_in_module(module_def_id, check_attr_visitor); if module_def_id.to_local_def_id().is_top_level_module() { check_attr_visitor.check_attributes(CRATE_HIR_ID, DUMMY_SP, Target::Mod, None); check_invalid_crate_level_attr(tcx, tcx.hir().krate_attrs()); } if check_attr_visitor.abort.get() { tcx.sess.abort_if_errors() } } pub(crate) fn provide(providers: &mut Providers) { *providers = Providers { check_mod_attrs, ..*providers }; } fn check_duplicates( tcx: TyCtxt<'_>, attr: &Attribute, hir_id: HirId, duplicates: AttributeDuplicates, seen: &mut FxHashMap, ) { use AttributeDuplicates::*; if matches!(duplicates, WarnFollowingWordOnly) && !attr.is_word() { return; } match duplicates { DuplicatesOk => {} WarnFollowing | FutureWarnFollowing | WarnFollowingWordOnly | FutureWarnPreceding => { match seen.entry(attr.name_or_empty()) { Entry::Occupied(mut entry) => { let (this, other) = if matches!(duplicates, FutureWarnPreceding) { let to_remove = entry.insert(attr.span); (to_remove, attr.span) } else { (attr.span, *entry.get()) }; tcx.emit_spanned_lint( UNUSED_ATTRIBUTES, hir_id, this, errors::UnusedDuplicate { this, other, warning: matches!( duplicates, FutureWarnFollowing | FutureWarnPreceding ) .then_some(()), }, ); } Entry::Vacant(entry) => { entry.insert(attr.span); } } } ErrorFollowing | ErrorPreceding => match seen.entry(attr.name_or_empty()) { Entry::Occupied(mut entry) => { let (this, other) = if matches!(duplicates, ErrorPreceding) { let to_remove = entry.insert(attr.span); (to_remove, attr.span) } else { (attr.span, *entry.get()) }; tcx.sess.emit_err(errors::UnusedMultiple { this, other, name: attr.name_or_empty(), }); } Entry::Vacant(entry) => { entry.insert(attr.span); } }, } }